Casting apparatus and method of operating the same



May 20 r924 1,49 ,869

R. W. SWEETNAM CASTING APPARATUS AND METHOD 0E OPERATING THE SAME filedNov. 12. 1921 2 Sheets-Sheet 1 May 20 1924. 1,494,869

R. W. SWEETNAM' CASTING APPARA-TUS Aim METHOD OF OPERATING THE SAMEFiled Nov. 12, 1921 2 Sheets-Sheet. 2

-- MVNTCR- 0 Patented May 20, 1924.

UNITED STATES] ROBERT W. SWEETNAM, OF TOLEDO, OHIO.

cas'rms APPARATUS AND METHon or OPERATING THE SAME.

Application filed; November 12, 1921-. Serial No. 514,511;

To all whom it may can com:

Be it known that I, ROBERT SWEETNAM, a citizen of the United EStates anda resident of Toledo, in the county of Lucas and State of Ohio, havemade an Invention Apperta-ining to Casting Apparatus and Methods ofOperating the Same; and I do-hereby declare the following to be afull,clear, and

exact description of the invention, such aswill enable others skilled inthe art to which it appertains to make and use the same, reference beinghad to the accompanying drawings, and to' the characters of referencemarked thereon, which form a part of this specification.

My invention has for its object to provide efficient means and methodfor reproducing in metal, forms of patterns. It particularly has for itsobject to accurately reproducedental forms embodied in wax patterns Theinvention may be carried out or embodied in structures of differentforms. To illustrate a practical application of the struc turecontaining the invention or wherein the invention may be performed Ihave selected one or two of such: constructions and shall describe themhereinafter. The apparatus. selected for purpose of illustration isshown in the accompanying drawings.

Figure 1 of the drawings illustrates a sectional view of a flask andparts containing my invention, and wherein the method of making dentalcastings also forming my invention may be carried out. Fig. 2 is-abottom view of the flask shown in Fig. 1 with the investment materialshown removed for purposes of illustration. Fig. 3, is a view lookingthrough the top before the investment material is pl'acedin-l the flask.Fig. 4 illustrates an asbestos lining that may be used for forming themouth of the sprue hole. Fig. 5 illustrates a tube for conducting aireither under atmospheric pressure or higher pressure to certain pointsin the investiment material and relative to parts of the matrix of themold. Fig. 6 illustrates a top view of a disc formed of materialimpervious to air and which moreover is a heat resisting material. Fig.7 is a broken enlarged view showinga part of a tubular frame forwithdrawing air from certainpoints within the investment material andwhich are located in certain positions relative to the matrix of themold. Fig. 8 illustrates the means for completely surrounding the matrixwith a zone of low air pressure condition. Fig.9 illustrates a View ofthe bottom of" the flask shown in Fig. 8. k i

l,- in Figs. 1 and is a dental flask that 1s supported in a shell 2 bymeans of the ridges or flanges 3 and 4 located at the: topof the flaskand the shell and so-as= to form the space" 5 between the flask: and theshell.

The flask 1 is provided with an inwardly extending'flange 6 on which islocated a disc 7 formed of a heat resisting material inrpervious to airand which wil l no't alloy or combine with the metal of whichthecastingis formed. The disc may be formed' of a vitrified porcelain materialhaving a high heat resisting character, that is, one that' will notcrack when subjectedlocally to the temperature of the molten metal fromwhich the casting is made, or it may be formed of a sheet metal that hasa melting or fusing point well above the" melting point of the metalused to form a casting and which will not alloy nor adhere to the metalof which the disc 7 is formed. Moreover thedisc must be formed of amaterial that will not permit air to pass through the disc and of amaterial wherein its outer edge may be seated. air tighten thefla n ge6. I preferably use" mica for forming the disc; Any suitable means maybe used in: order to secure the disc 7 inposition-'while the" flask isbeing filled with investment material. In the construction shown the)disc' 7 is secured in position by means ofth'e spring ring 8 thatfrictionally engages the inner surface of the flask 1: to hold :the disc7 in position on the flange 6;

The disc 7 if desired may be provided with one or more notches 9 andthe'flange 6 may be provided with the openings 10'. Before theinvestment material is inserted in the flask one or more tubular members121 may be inserted through the openings 10 formed in the flange 6.Preferably the tubular members ll tightly fit the openings 10. They areheld in position by the flange 61 They extend to near the upper end; ofthe flask and particularly to a point located near the upper surface orabove the investmentmaterial as finally formed in the flask. The lowerendsof the tubular members 11 preferably extend upwards and are locatedat apoint in proximity to the pointedparts of the matrix 31 andpreferably at points within the lines of. projection of the ma trixextending at right angles to. the plane of the bottom of the flask. Oneor more may extend between extensions, if any, of the matrix. Both endsof each of the tubes are so located in the investment and relative tothe upper surface and the matrix as to regulate the blow or flow of theair, and thus regulate the cooling. and consequently stretching ordrawing effect. This results from the difference in the air pressureproduced in the different parts of the flask, and particularly theinvestment.

The pattern is supported on a sprue pin 12 that extends through a hole13 formed in the disc 7. If it is desired to make two or more castingsin the same flask at the same time it may be done by inserting the samenumber of sprues through openings formed in the disc 7 The sprues andthe patterns may temporarily be secured in position by the use ofsuitable material, such as the wax 14:. When the investment material-hasbeen poured the sprue pin is removed in the manner well known in theart, and the mouth 15 of the sprue hole is formed by removing a portionof the investment material or by forcing a cone shaped asbestos disc 16around the sprue 12 before it is removed. The disc. 16 may besubsequently removed from the investment material thus formed or it maybe left in the investment material to assist in localizing the pressureon the molten metal to direct it with pressure through the sprue hole17.

Before the investment material is poured or inserted into the flask 1 atubular frame 18 having openings 19 and 20 may be supported on shorttubes 21 that extend through openings formed in the flask 1 preferablynear the flange 10 and thus communication is established from theexterior of the flask 1 to the openings 19 and 20 formed in the tubularframe 18 and at the same time the frame 18 is held in position. Theframe 18 may be formed of a pair of upright parts 33 and a pair ofcircular parts 3-1, 35 so arranged that the uprights and thetransversely extending parts communicate with each other. The frame 18substantially surrounds the pattern or the cavity and so that when theair pressure within the frame is reduced it produces a zone of low airpressure about the matrix and the molten metal that may be inserted inthe matrix.

lVhen the tubular parts, the disc and the pattern, are properlysupported, the portion of the flask on the pattern side of the disc isfilled with the investment material and allowed to at least partiallysolidify. The upper portion of the flask, that is, the portion above thedisc, is likewise filled with investment material and the mouth aboutthe upper endof the sprue pin is formed and the sprue pin may bewithdrawn. To prevent the investmentmaterial from entering the tubularmembers the openings may be closed by a disappearing material, suchas-wax or plugs of other material.

lNhen the investment material has become properly set the flask may beheated so as to' cause the wax contained. in the pattern and used forplugging the openings of the tubular members to be burned out, wherebythe opening will be formed and communication will be established betweenthe tubular members and through the porous investment inaterial for themovement of the air. The flask l is then placed in the shell 2 and theyare supported on a suction plate 22 in the manner well known in the art.Air is then drawn from the shell 2 while at the same time gold placedwithin the mouth of the sprue hole may be melted by means of a blowpipe. The suction produced will draw the air from the tubular frame 18and will form a low pressure zone about the vmatrix of the mold so thatas the metal is melted it will pass down through the sprue hole and fillall of the space within the matrix. Since the disc 7 closes off theadvent of any air around the sprue hole or to the frame through theinvestment material located in the upper end of theflask the moltenmetal, such as gold, will be forced by the atmospheric pressure into thesprue hole and into the matrix. The tubular members 11, how ever,conduct air to points near the extremities of the matrix and preferablybetween the lower extremities of the matrix and this air will difl'useitself radially towards the low pressure areas or portions within theflask. Inasmuch as the tubular members 11 terminate near the lowerextremities of the matrix there will be a blow from the ends of thetubes in all directions but the blow across the extremities will begreater if the ends of the tubular members 11 are properly placed. Thisoperates to chill the extremities and causes them to solidify within theextremities of the matrix while the remainder of the metal is in amolten or in :i highly malleable or ductile condition. The lower ends orextremities of thecast being fixed by the chilling and the molten metalbeing drawn in by the suction produced about the cast, it willpractically overcome the effect of the shrinkage by reason of thedifference of pressure produced on the molten gold in the sprue hole andthe molten or plastic or easily ductile gold Within the matrix and as itis drawn by the difference of pressure and cooled by the blow the moltenmetal solidifies and has a size substantially the same as that of thematrix whereby the ordinary shrinkage of the casting is practicallyobviated.

If it is desired to subject the gold in the sprue hole and the air inthe tubular members 11 to a pressure greater than at1nospheric pressure,a pressure plate 23 may be placed on the upper end of the shell 2 andany desired pressure may be produced within the top of the flask.

If it is desired to completely envelop the matrix and the casting with alow pressure zone it may be done by the use of the apparatus illustratedin Figs. 8 and 9. In this connection, if desired, a second frame 18position by a locking ring 25 that may be held in position by suitablelugs, such as the bayonet lugs 2.6 that engage the radially extendinglugs 29. The central area of the disc may also be used to contribute tothe formation of the low pressure zone by forming holes 30 in anydesired number in the disc 24. If desired the ring may be strengthenedby forming the spider 36 integral therewith.

I claim:

1. The method of making castings, which consists in chilling theextremities of the casting while subjecting other portions of thecasting before the metal in the said portions sets to less thanatmospheric pressure, and forcing the said metal in said portions by apressure greater than the first described pressure.

2. In a casting apparatus, a. flask, a mica disc supported on the flaskand having an opening through which molten metal may pass.

3. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, a mica disc seated onthe flask and having an opening through which the metal may pass.

4. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, a disc impervious to airand enclosed in portions of the investment material surrounding thesprue.

5.v In a casting apparatus,'a flask, a mica disc supported on the flaskand having an opening the size of the sprue hole'at which the disc islocated through which the metal may pass.

6 Inv a casting apparatus comprising a flask having investment materialand a: matrix formed in; the investment material, a. disc impervious toair and enclosed in portions of the investment material surroundmg thesprue, and having an opening of the: sizeof the sprue at the point thatthe disc is located through which the molten metal may pass, and havingsubstantlally anair sealing fit near its periphery witlrthe wall of theflask.

'7. In a casting apparatuscomprising a flask having investment materialand a matrix formed in the investment material, a disc impervious to airand enclosed in the investment material surrounding the sprue, andhaving an opening of the size of the sprue at the point that the disc islocated, through which the molten metal may pass, and havingsubstantially an air sealing fit near its periphery with the wall of theflask,

and means for reducing the air the bottom of the flask.

8. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, a

pressure at mica disc enclosed in the: investment material and locatedabove the matrix, and;

havingan air sealing flt with the flask, and having an opening throughwhich the molten metal may pass to the matrix, the size of the openingbeing substantially the same size as the sprue at the point along thesprue at which the disc is located, and means for reducing the airpressure at the bottom of the flask.

9; In a casting apparatus comprising a flask having investment materialand a ma.- trix formed in the investment material, the flask havingopenings and the investment material having passageways formed thereinthat substantially surround the matrix and communicate with the exterioroflthe flask through the said openings, a. shell for enclosing theflask, and means for reducing the air pressure within the shell and within the tubular passageways formed in the investment material.

10. In a; casting apparatus comprising a flask having investmentmaterial and a matrix formed in the investment material, the flaskhaving openings and the investment material having passageways formedthere in that substantially surround the matrix and communicate with theexterior of the flask through the said openings, a shell for enclosingthe flask, and means for reducing the air pressure within the shell andwithin the tubular passageways formed in the investmentmaterial, a discimpervious to air to air covering the matrix and the tubularpassageways, the investment material having a tubular passagewayextending to the lower corners of the matrix from the upper end of theflask, and unclosed by the shell.

12. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, the flask havingopenings and the investment material having passageways formed thereinthat substantially surround the matrix and communicate withthe exteriorof the flask through the said openings, a shell for enclosing the flask,and means for reducing the air pressure within the shell and within thetubular passageways formed in the investment material, a disc imperviousto air covering the matrix and the tubular passageways, the investmentmaterial having a tubu lar passageway extending to the lower corners ofthe matrix from the upper end of the flask, and unclosed by the shell.

13. In a. casting apparatus. comprising av flask having investmentmaterial and a matrix formed in the investment material, the flaskhaving openings and the investment material having passageways formedtherein that substantially surround the matrix and communicate with theexterior of the flask through the said openings, a shell for enclosingthe flask, and means for reducing the air pressure within the shell andwithin the tubular passageways formed in the investment material, amica. disc covering the matrix and the tubular passageways.

14. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, the flask havingopenings and the investment material having passageways formed thereinthat substantially surround the matrix and communicate with. theexterior of the flask through the said openings, a shell for enclosingthe flask, and means for reducing the air pressure within the shell andwithin the tubular passageways formed in the investment material, a micadisc covering the matrix and the tubular p assageways, the investmentmaterial having a tubular passageway extending to the lower corners ofthe matrix from the upper end of the flask, and unclosed by the shell.

15. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, the flask havingopenings and the investment material having passageways formed thereinthat substantially surround the matrix and communicate with the exteriorof the flask through the said openings, a shell for enclosing the flask,and means for reducing the air pressure within the shell and within thetubular passageways formed in the investment material, a mica disc covering the matrix and the tubular passageways, the investment materialhaving a tubuflask having investment material and a.

matrix formed in the investment material, the flask having openings andthe investment material having passageways formed therein thatsubstantially surround the matrix and communicate with the exterior ofthe flask through the said openings, a shell for enclosing the flask,and means for reducing the air pressure within the shell and within thetubular passageways formed in the investment material, a disc imperviousto air and enclosed in the investment material and fitting the wall ofthe flask and having an opening through which the molten metal may pass.

7 17 In a casting apparatus comprising a flask having investmentmaterial and a matrix formed in the investment material, the flaskhaving openings and the investment material having passageways formedtherein that substantially surround the matrix and communicate with theexterior of the flask through the said openings, a shell for enclosingthe flask, and means for reducing the air pressure within the shell andwithin the tubular passageways formed in the investment material, a discimpervious to air and enclosed in the investment material and fittingthe wall of the flask and having an opening through which the moltenmetal may pass.

18. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, the flask havingopenings and the invest ment material iaving passageways formed thereinthat substantially surround the matrix and communicate with the exteriorof the flask through the said openings, a shell for enclosing the flask,and means for reducing the air pressure within. the shell and within thetubular passageways formed in the investment material, a disc imperviousto air and enclosed in the investment material and fitting the wall ofthe flask and having an opening through which the molten metal may pass.

19. In a casting apparatus comprising a flask, having investmentmaterial and a matrix formed in the investment material, the flaskhaving openings and the investment material having passagewaysformedtherein. that substantially surround the matrix and communicate with theexterior of the flask through the said openings, a shell for enclosingthe flask, and means for reducing the air pressure within the shell andwithin the tubular passageways formed in the investment material, a micadisc enclosed in the investment material and fitting the wall of theflask and having an opening through which the molten metal may pass, theopening having a size the same as the size of the sprue hole at thepoint at which the disc is located.

20. In a casting apparatus ing a flask having investment material and amatrix formed in the investment material, the flask having openings andthe investment material having passageways formed therein thatsubstantially surround the matrix and communicate with the exterior ofthe flask through the said openings, a shell for enclosing the flask,and means for reducing the air pressure within the shell and within thetubular passageways formed in the investment material, a mica discenclosed in the investment material and fitting the wall of the flaskand having an opening through which the molten metal may pass, theopening having a size the same as the size of the sprue hole at thepoint at which the disc is located.

21. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, the flask havingopenings and the investment material having passageways formed thereinthat substantially surround the matrix and communicate with the exteriorof the flask through the said openings, a shell for enclosing the flask,and means for reducing the air pressure within the shell and within thetubular passageways formed in the investment material, a mica discenclosed in the investment material and fitting the wall of the flaskand having an opening through which the molten metal may pass, the opening having a size the same as the size of the sprue hole at the point atwhich the disc is located.

22. In a casting apparatus comprising a flask having investment materialand a matrix formed in the investment material, the flask havingopenings and the investment material having passageways formed thereinthat substantially surround the matrix and communicate with the exteriorof the flask through the said openings, a shell for enclosing the flask,and means for reducing the air pressure within the shell and within thetubular passageways formed in the investment material, a. mica discenclosed in the investment material and fitting the wallof the flask andhaving an opening through which the molten metal may pass, the openinghaving a size the same as the size of the sprue hole at the point atwhich the disc is located, the lower end of the flask covered by a discimpervious to air.

comprisand" communicate with the exterior of the flask through the saidopenings, a shell for enclosing the flask, and means for reducing theair pressure within the shell and within the tubular passageways formedin the investment material, a mica disc enclosed in the investmentmaterial and fitting the wall of the flask and having an opening throughwhich the molten metal may pass the opening having a size the same asthe size of the sprue hole at the point at which the disc is located,the lower end of the flask covered by a disc impervious to air, andhavingone or more openings located in the central portion of the disc.

24:. In a casting apparatus, a flask having an inwardly extendingflange, a disc impervious to air supported on the flange, the flaskhaving openings located below the flange and a tubular frame secured inproximity to the openings and communicating with the exterior of theflask through the openings.

25. In a casting apparatus, a flask having an inwardly extending flange,a disc impervious to air supported on the flange, the flask havingopenings located below the flange and a tubular frame secured inproximity to the openings an communicating with the exterior of theflask through the openings, tubes supported by the flange and locatedwithin the flask. 1

26. In a casting apparatus, a flask having an inwardly extending flange,a mica disc having an opening the size of the sprue hole and supportedon the flange.

27. The method of producing castings, which consists in forming a lowair pressure zone in vicinity of the matrix and moving air across thelower extremities of the metal in the matrix.

28. The method of producing castings, which consists in forming a lowair pressure zone in proximity to the lower side of the matrix andmoving air across the lower extremities of the metal in the matrix whilethe metal in the mold is subjected to a pressure greater than that ofthe zone.

29. The process of forming castings in investment material, whichconsists in moving air across the lower extremities of the metal in thematrix.

In testimony whereof, I have hereunto signed my name to thisspecification.

ROBERT w. SWEETNAM.

